Systems supporting exciton-polaritons represent solid-state optical platforms with a strong built-in optical nonlinearity provided by exciton–exciton interactions. In conventional semiconductors, ...with hydrogen-like excitons, the nonlinearity rate demonstrates the inverse scaling with the binding energy. This makes excitons that are stable at room temperature weakly interacting, which obviously limits the possibilities of practical applications of the corresponding materials for nonlinear photonics. We demonstrate, experimentally and theoretically, that these limitations can be substantially softened in hybrid perovskites, such as MAPbBr3, due to the crucial role of the polaron effects mediating the interparticle interactions. The resulting exciton-polaron-polaritons remain both stable and strongly interacting at room temperature, which is confirmed by large nonlinear blueshifts of lower polariton branch energy under resonant femtosecond laser pulse excitation. Our findings open novel perspectives for the management of the exciton-polariton nonlinearities in ambient conditions.
Abstract
Currently, halide perovskites are very perspective materials not only for photovoltaics but also for nanophotonic and especially nonlinear optics. These materials have already demonstrated ...high two-, three- and many- photon absorption coefficients, strong Kerr-nonlinearity, and high-efficient second harmonic generation. Easy and cheap fabrication gives halide perovskites a wide area for scientific research and engineering applications. However, to achieve the stability of perovskites is still a challenging task, which scientific community is working on. In this work, we study a new form of encapsulation of perovskite nanoparticles in sub-micron porous dielectric nanospheres. Due to small pores in such spheres, perovskites are not only protected from external factors, but also are confined in size, which brings several features in the photoluminescence emission. We also show resonant properties of spherical sub-micron particles, which can be used for enhancing upconversion photoluminescence intensity.
•First report of inkjet printing of holographic multi-color image was performed by one type of pigment-free ink on a volume Bragg grating.•Selectivity of Bragg grating shifts toward the long ...wavelength region depending on ink dosage because of swelling rating of material.•Two mechanisms of droplet deposition, precise control of ink dosage, and influence on swelling rating was described.•The study showed absence of chemical interaction between ink composition and substrate with volume Bragg grating.
Despite the rapid progress in various holographical technologies, development and miniaturization, the fabrication of individual design holographic images is still a complicated, costly, time- and labor-consuming process. This research proposes a novel inkjet printing method for obtaining multiple color holographic images based on applying a physical impact on a volume Bragg grating recorded by the interference of counterpropagating plane waves in a commercially available photopolymer material. Inkjet printing technique allows cost-effective, rapid, and reproducible fabrication of high-resolution (≥ 600 dpi) holographic patterns. A specific printable ink composition consisting of monomers in combination with the photoinitiators penetrates the polymer matrix and leads to the swelling of the material. This causes an increase in the period of the recorded grating and visually observed color change of the resulting hologram. Precise control over the ink dosage allows exact shifting of wavelength (∼30 nm for single layer at drop spacing of 50 μm). The printing parameters can be adjusted towards the optimal conditions for obtaining the final image with high quality.
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The outstanding optical properties and multiphoton absorption of lead halide perovskites make them promising for use as fluorescence tags in bioimaging applications. However, their poor stability in ...aqueous media and biological fluids significantly limits their further use for in vitro and in vivo applications. In this work, we have developed a universal approach for the encapsulation of lead halide perovskite nanocrystals (PNCs) (CsPbBr3 and CsPbI3) as water-resistant fluorescent markers, which are suitable for fluorescence bioimaging. The obtained encapsulated PNCs demonstrate bright green emission at 510 nm (CsPbBr3) and red emission at 688 nm (CsPbI3) under one- and two-photon excitation, and they possess an enhanced stability in water and biological fluids (PBS, human serum) for a prolonged period of time (1 week). Further in vitro and in vivo experiments revealed enhanced stability of PNCs even after their introduction directly into the biological microenvironment (CT26 cells and DBA mice). The developed approach allows making a step toward stable, low-cost, and highly efficient bioimaging platforms that are spectrally tunable and have narrow emission.
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